Original title: Characterizing Large Scale Quantum Systems with Error Per Circuit Layer
Travis Hurant, Arian Vezvaee, Swarnadeep Majumder, Aniket Dalvi +2 · September 2026
Testing quantum computers is tricky. Small errors pile up across interacting operations, but current tests often require hard classical simulations, strict gate sets, or looking only at small pieces of the system. To solve this, researchers introduced Error Per Circuit Layer, or EPCL. The method runs the exact same random circuit on two separate quantum registers on the device. Then, it measures how much the two final quantum states overlap across different circuit depths. As circuits get deeper, noise causes this overlap to fade away. By tracking this decay, EPCL estimates error rates without needing classical simulation of the right answers or reset steps back to a known state. It works with arbitrary gate sets, including non-Clifford gates. Simulations showed it accurately tracks noise, and physical experiments on IBM quantum hardware successfully demonstrated clear EPCL decay using 8- and 16-qubit implementations.
Two chefs cook the same recipe from memory in separate kitchens. Without mistakes, they produce identical dishes, but each small error in measurement or timing adds up. After many steps, the dishes start tasting different, and comparing them reveals how often errors occur. Here, the two quantum registers run identical circuits, and measuring their output overlap shows how errors accumulate per layer.
Quantum researchers need a way to fairly compare systems as they grow larger, but current benchmarks are slow or restrictive. EPCL measures error directly from the system without requiring a perfect simulation, making testing more practical.
The method relies on assumptions about noise models, such as depolarizing noise, and may require additional techniques like Pauli twirling for coherent errors. Experiments so far are limited to 8 and 16 qubits on IBM hardware, not larger systems. Inter-register correlations can affect measurements, adding complexity.
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Characterizing Large Scale Quantum Systems with Error Per Circuit Layer — Travis Hurant, Arian Vezvaee, Swarnadeep Majumder et al.
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.